1. Field of the Invention
The present invention relates to organic light-emitting display panels containing a matrix of organic light-emitting elements, to display devices, and to methods of manufacturing organic light-emitting display panels.
2. Description of the Related Art
In recent years, organic light-emitting display panels that have a plurality of organic light-emitting elements in rows above a substrate have been used as light-emitting display panels in compact electronic equipment and compact display devices. The basic structure of an organic light-emitting element is to form a light-emitting layer, which includes organic light-emitting material, between a pair of electrodes, i.e. an anode and a cathode. When voltage is applied between the pair of electrodes, holes injected into the light-emitting layer from the anode recombine with electrons injected into the light-emitting layer from the cathode, and as a result, the organic light-emitting element emits light. Since each organic light-emitting element in the organic light-emitting display panel emits light, the light from the display panel is highly visible.
In an organic light-emitting display panel, typically a light-emitting layer is partitioned in each organic light-emitting element by banks (walls) formed from insulating material. These banks define the shape of the light-emitting layer. Between the anode and the light-emitting layer, intermediate layers are provided as necessary, such as a hole-injection layer, hole transporting layer, hole injection and transporting layer, or an electron blocking layer. An electron injection layer, electron transport layer, or electron injection and transporting layer may also be provided between the cathode and the light-emitting layer as necessary.
In a full-color organic light-emitting display panel, such organic light-emitting elements are formed into sub-pixels whose color is R, G, or B. Three adjacent RGB sub-pixels together constitute one pixel.
In order to form the light-emitting layer or intermediate layers in each organic light-emitting element, banks are formed on the substrate to partition adjacent organic light-emitting elements. Subsequently, an inkjet or other wet method is generally used to spray ink containing high-molecular (polymer) material or low-molecular material suitable for thin-film formation. With such a wet method, it is relatively easy to form the intermediate layer or light-emitting layer even in large panels.
In an inkjet method (see Patent Literature 1), which is representative of wet methods, inkjet heads are moved across a substrate, on which ink is to be sprayed, in any direction of the matrix of elements while a solution (hereinafter simply “ink”) is sprayed by ejecting drops of ink through each nozzle into regions defined by the banks on the substrate. The ink contains organic material and solvent that are for forming the intermediate layers, the light-emitting layer, etc.
3. Patent Literature    Patent Literature 1: Japanese Patent Application Publication No. 2003-241683